I guess it depends on your level of knowledge and what you want to learn as well as the format. Crypto online courses don't seem to be particularly popular. However, Coursera offers a range of Bitcoin-related courses, actually, which you can see here. I think that YouTube videos, this forum, and articles are enough to get a general idea and be up-to-date on what's happening in the world that might have an impact or is directly related to Bitcoin. I think that for intro level top-5 by relevance on Youtube is quite okay. There's also Bitcoin wiki and Investopedia. Good luck!